Air conditioning apparatus



3 Sheets-Sheet 1 Filed July 31, 1959 INVENTOR. JOHN SCARR JR.

ATTORNEY July 31, 1962 J. SCARR, JR 3,047,273

AIR CONDITIONING APPARATUS Filed July 51, 1959 5 Sheets-Sheet 2 F/GZ xAAA,

NIGHT DAY FIG /0 INVENTOR. JOHN SCA RR JR. BY

ATTORNEY July 31, 1962 .1. SCARR, JR 3,047,273

AIR CONDITIONING APPARATUS Filed July 31, 1959 5 Sheets-Sheet 5 NOV ACINVENTOR.

JOHN SCARR JR.

BY /W ATTORNEY United States Patent 3,047,273 AIR CONDITIONING APPARATUSJohn Scarr, In, Penn Hills Township, Allegheny County,

Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., acorporation of Delaware Filed July 31, 1959, Ser. No. 830,897 3 Claims.(Cl. 257--287) The instant invention relates to automatic airconditioning apparatus, and more particularly pertains tothermostatically controlled apparatus entirely automatic in operationfor supplying heated air to the air conditioned space whenever thetemperature therein falls below a predetermined value and for supplyingcool air to such air conditioned space whenever the temperature thereinis above a higher predetermined value. More specifically, the apparatusinvolves an electrical control system for operating, in accordance withthe previously mentioned temperature levels, a combined heating andcooling unit of the type that serves its heating function upon a highlevel of burner output and which serves its cooling function upon a lowlevel of burner output by the application of absorption-typerefrigeration principles. Such combined heating and cooling units are inthemselves well known in the art, as exemplified by the commerciallyavailable Servel air conditioning equipment bearing model designationsXFC96-G and FCA- 96-G shown and described in detail in a brochurepublished by Servel, Inc. Other concerns manufacture functionallysimilar The present invention has applicability to automaticallycontrolling the operation of combined heating and cooling units of thetype specified when the latter are gas fired (as are the above-notedServel models); however, the invention is particularly concerned withautomatically controlling the operation of such units when the latterare adapted to be oil fired, such as by commercially available oilburnerunits (such as the well known Heil burner) provided with anadjustable fuel oil metering device such as the Sundstrand Model ATair-oil fuel unit. Extension of the application of the principles of theinvention to oil-fired as well as gas-fired units makes possibleenjoyment of year-round air conditioning in areas where mains fornatural or artificial gas are nonexistent. It will be evident to thoseskilled in the art that the principles of the invention will beapplicable to the use of LPG. fuels in the same manner as to gas-firedunits, such fuels of course being available in areas where gas mains arenonexistent; however, this fact does not reduce the importance of beingable to use oil as fuel considering the difference in expense involvedin providing storage for L.P.G. fuels and fuel oil and also the pricedifferentials existing between such fuels.

Broadly, in relation to oil-fired units, the invention involveselectrical means for selectively metering oil to an oil burner at eithera high or a low rate with corresponding adjustment of the rate at whichair is supplied to the burner, and also for shutting off the supply offuel oil and air to the burner entirely; such selective means beingelectrically controlled by an electrical system that includestemperature responsive switches and associated circuitry such thatwithin a predetermined temperature range the supply of air and fuel tothe burner is cut off and with the air and fuel being supplied at thehigh and low rates to the burner when the temperature is below and abovesuch range of temperature, respectively.

The selective operation of the rate of supply of fuel oil and air to theburner is accomplished by de-energizing the source of oil and air whenit is desired that the supply of Oil and air be cut off; and employing asolenoid actuated mechanical linkage to jointly control the metering offuel oil and an air control shutter to achieve either the high or lowlevel of burner ouputs when the oil and air sources are energized. Meansis provided for energizing a pump for circulating a cooling fluidthrough a condenser or heat exchanger conventionally associated with theabsorption refrigeration system whenever the burner system isselectively operated for low burner output, and additionally means isprovided for circulating or blowing cooled air into the air conditionedspace concurrently with the operation of the pump for circulating thefiuid coolant through the condenser.

The electrical control system includes a pair of mercury switches, eachof such switches being a single-pole, double-throw switch. The mercuryswitches are provided with a common temperature responsive actuator,such mercury switches being angularly inclined with respect to eachother relative to their axis of temperature controlled rotation, thearrangement being such that throughout a particular range of rotation ofthe switches such switches are closed at their opposite ends withangular displacement of the mercury switches either above or below suchrange of angles resulting in the adjacent ends of the mercury switchesbeing closed. One pair of adjacent ends of the switches is associatedwith electrical circuitry for operating the system for a heating cycle,with the other pair of adjacent ends of the mercury switches beingassociated with electrical circuitry for causing a cooling cycle. Themercury switches are associated in such a manner that when they occupy aposition within the range of angles in which opposite ends of theswitches are closed, the system is inactive insofar as either heating orcooling is concerned.

Means is provided for angularly adjusting the mercury switches withrespect to each other so that the temperature range in which the systemis to be inactive insofar as heating or cooling is concerned can beadjusted. Also, means is provided allowing adjustment of suchtemperature range upwardly or downwardly as desired without disturbingthe extent of the temperature range itself.

The invention will be best appreciated upon reference to theaccompanying drawings illustrative of a preferred embodiment thereofapplied to the automatic operation of a heating and cooling unit of theServel type modified for oil firing, wherein:

FIGURE 1 is a diagrammatic illustration of the invention showing thesame applied for air conditioning a room in a dwelling;

FIGURE 2 is a simplified diagrammatic illustration of the electricalcomponents of the air conditioning system;

FIGURE 3 is a perspective view of the solenoid actuated controlmechanism for controlling the rate of supply of oil and air to theburner;

FIGURE 4 is a perspective view of the adjustable mounting means for themercury switches and the temperature-sensitive actuating means therefor;

FIGURE 5 illustrates diagrammatically the angular adjustment between themercury switches through the use of the means shown in FIGURE 4;

FIGURES 6 through 8 illustrate respectively the positions occupied bythe mercury switches when the system is effective for heating, inactive,and effective for cooling when considered in relation to FIGURE 9;

FIGURE 9 is a schematic wiring diagram of the entire electrical controlsystem; and

FIGURE 10 is an idealized graphical representation of the manner inwhich the temperature in the air conditioned space can vary as thecontrol system operates from a condition necessitating intermittent heatsupply followed by the necessity for intermittent cooling.

Referring to FIGURE 1, the reference numeral 10 designates a domesticdwelling generally that is shown partially in section to expose aportion of an upstairs room 12 that is air conditioned by the apparatushereinafter described, and a portion of a basement 14 in which the bulkof the air conditioning equipment is disposed. The reference numeral 16designates generally a Servel Model FCA96G air conditioning (combinedheating and cooling) unit disposed in the basement 14, such unit 16being of the type that heats air Whenever supplied heat at a rateexceeding a predetermined value, but which will cool air upon beingsupplied heat at a predetermined lower value. An air duct 18communicates between the unit 16 and the interior of the room 12 forsupplying air from the unit 16 to the room 12 that is either heated orcooled by the unit 16 as the case may be. A return air duct 20communicates between the interior of the room 12 and the bottom of theunit 16. It will be appreciated that the unit 16, the duct 13, the room12, and the duct 20 constitute a closed air circuit. Under the controlof the system presently to be described, an air blower actuated by anelectric motor 22 is provided in the duct 20 for forcing movement of airthrough such circuit, which circulated air may be either unaffected,heated or cooled during its passage through the unit l6.

A thermostat 24 described more fully hereinafter is placed on a wall 26of the room 12, such thermostat 24 being connected to a masterconditioner control panel 23.

The unit 16 is provided with a fluid coolant circulatory system thatincludes a condenser 32 positioned outside the dwelling 10, with thepiping associated with the condenser 32 including a portion disposedwithin the basement 14 that is provided with a circulating pump that isactuated by an electric motor 34, it being understood that when themotor 34 is energized, the cooling medium will be circulated from theunit 16 through the condenser 32 and back to the unit 16, whereby heatcan be removed from the refrigerating system of the unit 16.

A burner system is designated generally at 36 and the same is associatedwith the lower part of the unit iii in lieu of the gas-fired unitcustomarily associated with the Servel Model No. FCA96G unit. Referringto FIG- URE 3, the burner system 36 is shown in perspective as a part ofthe heating and cooling unit 16. The burner system 36 is a Heil burnerthat includes a Sundstrandtype oil pump 38. The pump 38 is conventionaland includes a pumping rate meter control shaft 46. The burner system 36also includes an air blower section 4-2, the air flow rate of which iscontrolled by a conventional gating valve 44 partially visible throughan adjustment slot 46 in the housing of the air blower section 42. Itwill be understood that the oil metering pump 38 and the motor for theair blower section 42 of the burner system 36 are provided with a pairof common electrical supply leads 48 and 49 that connect between themaster panel 28 and the burner 36 (see FIGURE 2), the arrangement beingsuch that when the leads 4% and 49 are energized, the oil metering pump38 and the blower of the air section 42 are both placed in operation.The rates at which the oil metering pump 38 and the blower section 42supply oil and air for combustion are controlled by means of the angularposition of the shaft 40 and the position occupied by the gating valveAs viewed in FIGURE 3, counterclockwise rotation of the shaft 40 resultsin a higher rate of oil supply with displacement of the gating valve 44downwardly towards the right resulting in a corresponding increase inthe rate of air supply through the blower section 42. With the shaft 40and the gating valve 44 in the positions shown thereof in FIGURE 3, therates of oil and air supply are balanced and are at rates such that alow level of heat output for the burner system 36 is realized. Such rateof low heat output for domestic purposes can conveniently be on theorder of about one-half gallon of fuel oil per, hour.

A common means is provided for actuating both the shaft 40 of the oilmetering pump 38 and the gating valve 44 in such a manner that asubstantially increased heat output for the burner system 36 isaccomplished (say on the order of one gallon per hour oil consumptionfor do mestic purposes) with the relative oil and air fiow rates beingappropriately balanced. Such common means for actuating the shaft 40 andthe gating valve 44 comprises a horizontal bar 5i) guided for verticalreciprocation, such bar 50 being resiliently biased to a raised positionby a coiled tension spring 51 that extends between the bar 5@ and abracket 52 mounted on the oil metering pump 38. An electrical solenoid54 is positioned below the bar 50 for actuating guided vertical movementof an armature 56 connected to the bar 5%. The arrangement is such thatthe bar Sil normally occupies the position shown thereof in FIGURE 3,but is displaced to a lowered position against the action of the spring51 upon energization of the solenoid 54. The shaft 46 of the oilmetering pump 38 is provided with an actuating arm 58 that is connectedby a link 66 to one end of the bar 56, the other end of the bar 59 beingconnected by a link 62 to the gating valve 44. It will therefore be seenthat by virtue of the mechanical linkages between the bar 50 and theshaft 40 and between the bar 50 and the gating valve 44, the heat outputof the burner system 36 is at a high level during energization of theburner system 36 through the leads 48 and 49 during the period of timethat the solenoid 54 is energized, but that when the leads 48 and 49 areenergized and the solenoid 54 is not energized, the heat output of theburner system 36 will be at a reduced level. It will be understood thatsuch high and low heat outputs of the burner system 36 correspond to theunit 16 operating on heating and cooling cycles, respectively.

Attention is now directed to FIGURE 4 wherein the temperature controlledcomponents of the thermostat 24 are shown. A temperature responsivebimetallic strip of spiral form is indicated at 64. As is conventional,the outer end of the bimetallic strip 64 can be adjusted angularlywithin the housing of the thermostat 24 by means of the control knob 66(see FIGURE 2) to an extent determined by appropriate indicia 68provided on the housing of the thermostat 24. The inner end of thebimetallic strip 64 is secured to a shaft 70. A pair of mercury switches72 and 74 are mounted on the shaft 70 in adjusted angular relationthereto. The angular adjustment is effected by means of collars '76 and78 fixed in adjusted relation to the shaft 70 by means of set screws 80and 82 that extend through the collars '76 and 78, respectively. Thecollars 76 and 78 are respectively provided with spring clips 34 and 86that resiliently hold the mercury switches 72 and 74. FIGURE 5 shows at88 an angle which may be effected by adjustment of the collars 76 and 78between the mercury switches 72 and 74.

Attention is now directed to FIGURES 6 through 8, inclusive. It will beseen that the mercury switch 72 includes end terminals 90 and 92, and acentral conductor 94 having its opposite ends adjacent the terminals 96and 92. The mercury switch 72 contains a small quantity of mercury 96which selectively shorts the conductor 94 to the terminals 96 and 92 ina manner dependent upon the horizontal inclination of the mercury switch72. Such inclination is, of course, determined by the adjustment of thethermostat knob 66 relative to the indicia 68 (this turns the bimetallicstrip 64 and the shaft 70 carried thereby as a unit), the adjustment ofthe collar 76 on the shaft 76', and the effect of temperature on thebimetallic strip 64. At temperatures below a minimum value T (say 70F.), the switch 72 is tilted counterclockwise so that the mercury 96electrically connects terminal 90 to the conductor 94 (see FIGURE 6),While at temperatures above T (see FIGURES 7 and S), the mercury 96electrically connects terminal 92 to the conductor 94. Switch 74 isidentical to switch '72 except for its angle of -3 inclination in thevertical plane indicated at 88 in FIG- URE 5. The switch 74 includesterminals 98 and 100, conductor 102, and mercury 104. At temperaturesbelow T (T being higher than T say 80 F.), the mercury 104 electricallyconnects the conductor 162 to the terminal 98 (see FIGURES 6 and 7), butat temperatures higher than T the mercury 104 electrically connects theconductor 102 to the terminal 100 (see FIG- URE 8). As showndiagrammatically in FIGURES 6 through 8, the conductors 94 and 102 ofthe switches 72 and 74 are electrically connected by a lead 186.

Attention is now directed to FIGURE 9 wherein the entire electricalsystem is schematically illustrated. The numerals 108, 110, 112, and 114respectively designate a master control relay, a burner control relay, ablower control relay, and a relay for selectively controlling the outputrate of the burner system 36 and the coolant circulating pump motor 34.In accordance with whether demand is for a heating or cooling cycle,actuation of the relays 108, 110, 112, and 114 is dependent upon theposition of the mercury switches 72 and 74. Circuitry will now bedescribed by means of which the solenoid 116 of relay 108 is energizedsolely when the switches 72 and 74 are in the position shown in FIGURE6; the solenoid 118 of relay 110 is energized solely when the switches72 and 74 are in either of the positions shown in FIGURES 6 and 8; andthe solenoid 120 of relay 114 is energized solely when the switches 72and 74 are in the position shown in FIGURE 8.

The relays 108, 110, 112, and 114 are included in the master panel 28that is fixed to the unit 16 (see FIGURE 1). Domestic alternatingcurrent (110 V. AC.) is supplied by leads 12-2 and 124 to the primary ofa stepdown transformer (24 v. A.C. output) 126. One terminal of thesecondary of the transformer 126 is connected to the terminal 90 ofswitch 72 through a thermostat heater 128, disposed in the housing ofthe thermostat 24, by a lead 130, with the other terminal of thesecondary of the transformer 126 being connected to solenoids 116 and118 by leads 132 and 134. For a purpose to be explained later, thelast-mentioned terminal of the secondary of the transformer 126 isconnected to the solenoid 136 of the relay 112 by a lead 138.

FIGURE 9 shows the electrical system in the condition corresponding tothe position of the switches 72 and 74 shown in FIGURE 7, in which casenone of the relays 108, 110, 112, and 114 have their solenoidsenergized, and the armatures of such relays and the armature actuatedcontacts thereof are shown in corresponding positions. The relay 108includes contacts 140 and 142 that are normally open and a contact 144that is normally closed. The contacts 140, 142, and 144 are carried byan armature 146. The relay 110 includes normally open contacts 148 and15 9 carried by an armature 152. The relay 112 includes a normally opencontact 154 carried by an armature 156. The relay 114 includes anormally open contact 158 and a normally closed contact 160 carried byan armature 162.

The end of the solenoid 116 remote from the transformer 126 is connectedto the terminal 98 of switch 74 by a lead 164. The previously mentionedtransformer lead 130 is connected to the terminal 100 of switch 74 by alead 166. It will therefore be apparent that solenoid 116 can only beenergized upon the switches 72 and 74 both being in the FIGURE 6position (temperature ambient to the thermostat 24 being less than T bya circuit comprising lead 132, transformer 126, lead 130, resistor 128,terminal 96', mercury 96, conductor 94, lead 106, conductor 182, mercury104, terminal 98, lead 164, and the solenoid 116.

The end of the solenoid 118 remote from the transformer 126 is connectedto the terminal 92 of switch 72 by a lead 168, and also to the ,lead 164by a lead 170 that can be closed by the relay contact 140. By virtue ofthe latter connection, it will be plain that the solenoid 118 isenergized by the action of the contact 140 whenever the solenoid 116 isenergized. Otherwise, the solenoid 118 can only be energized when theswitches 72 and 74 are as shown in FIGURE 8 (temperature ambient to thethermostat 24 being in excess of T by the circuit comprising lead 134,transformer 126, lead 130, lead 166, terminal 100, mercury 104,conductor 182, lead 106, conductor 94, mercury 96, terminal 92, lead168, and the solenoid 118.

While relays 108, 110, and 112 are actuatable by 24 v. A.C., relay 114,and the solenoid 54 are actuatable by V. AC. The solenoid of relay 114is connected in series between power supply leads 122 and 124, by leads170, 172, 174, and 176, with connection between leads 172 and 174 beingmade by contact 142 on actuation of relay 108, and with connectionbetween leads 174 and 176 being made on actuation of relay 110.Therefore, relay 114 is actuated solely upon concurrent actuation ofrelays 108 and 110 which can only occur when the switches 72 and 74 areas shown in FIG- URE -6 (temperature ambient to the thermostat 24 beingless than T The burner system 36 is connected in series between theleads and 174 by the leads 48 and 49 so that the burner 36 iselectrically energized for ignition, supplying combustion air, oil, etc.solely when relay 110 is actuated, in other words, solely when theswitches 72 and 74 are in the positions shown in FIGURES 6 and 8(temperature ambient to the thermostat 24 being either above T or lessthan T The pump motor 34 for circulating coolant through the condenser32 is connected in parallel with the burner system 36 by leads 178 and188; however, the leads 178 and 186 are connected by the contact 160solely when the relay 114 is not actuated. Therefore, the pump motor 34is actuated solely when the switches 72 and 74 are as shown in FIGURE 8(the temperature ambient to the thermostat 24 being above T Thepreviously mentioned solenoid 54, associated with the burner system 36for controlling the rate of fuel and air supply, and consequently theheater output rate, is connected in parallel with the solenoid 120 ofthe relay 114- by leads 182 and 184. The leads 182 and 184 are connectedby the contact 158 solely when the relay 114 is actuated, andconsequently the burner system 36 is changed from its normal low heatoutput adjusted posi-' t-ion by action of the solenoid 54 to the highheat output adjusted position when the relay 114 is actuated (thetemperature ambient to the thermostat 24 being below T Energization ofthe solenoid 136 of relay 112 is made dependent upon several factors,the first of which is a conventional temperature responsive single-pole,doublethrow switch 186 associated with the unit 16 so as to sense thetemperature of treated air therein. Such switches are commonly used withautomatically controlled furnaces and serve with a snap action to throwthe switch in one direction when the temperature of the furnace a-irexceeds a moderately high value in excess of desired room temperature,say about 110 F., with the switch being thrown in the other direction atall lower temperatures. The single pole 188 of the switch 186 isconnected by a lead 190 to the end of the solenoid 136 opposite thetransformer 126, and the movable contact 192 is shown in the latterposition (low or cool air temperature in the unit 16) connecting betweenthe pole 188 and stationary contact 194. At temperatures above apreselected minimum, the contact 192 connects between the pole 188 and astationary terminal 196, in which latter case the solenoid 136 isenergized by virtue of a lead 198 connected between the terminal 196 andthe lead 130, thereby completing a circuit through the secondary of thetransformer 126 comprised of lead 190, contact 192, terminal 196, lead198, lead 130, transformer 126, lead 138, and solenoid 136.

The terminal 194 of the switch 186 is connected by a lead 200 to thepole 282 of a manually operated singlepole, double-throw switch 264. Theswitch, as shown in FIGURE 2, is mounted on the housing of thethermostat 24:, and the two fixed contacts 266 and 2955 of the switch204 are respectively labeled auto and on. With the movable contact 210of the switch 2% being in the on position, the solenoid 136 will beenergized notwithstanding the position of the contact 192 of switch 186,as the terminal 208 of switch 2 is (like terminal 196 of switch 186)connected by a lead 212 to the lead 130.

With the contacts 192 and 210 of switches 186 and 284 positioned asshown in FIGURE 9, the solenoid 136 can only be energized by a circuitthat includes a lead 214 (connected to terminal 266 of switch 2%), leads216, 218, and 168, terminal 92, mercury 96, conductor 94, lead 106,conductor 102, mercury 104, terminal 1%, leads 166 and 130, transformer126, lead 138, solenoid 136, lead 1%, pole 188, contact 192, terminal1%, lead 2%, pole 292, contact 210, and terminal 2ii6.The latter circuitcan only be cooled by contacts 144 and 156 when relay 168 is notactuated and relay 1-10 is actuated (this occurs solely when thetemperature ambient to the thermostat 24 exceeds T in which case theswitches 72 and 74 are in the position shown in FIGURE 8). Therefore,the relay 112 is actuated solety when either:

(1) Temperature in the unit 16 exceeds a predetermined value, or

(2) Temperature in the unit 16 is below said predetermined value and thecontact 210 engages the terminal 203 labeled on, or

(3) Temperature in the unit 16 is below said predetermined value, thecontact 210 engages the terminal 266 labeled auto, and the temperatureambient to the thermostat 24 exceeds T The electric blower motor 22 forcirculating air is connected between the power lead branches 1'74] and176 by leads 220, 222, and 224, it being noted that the contact 154serves to connect leads 222 and 224 solely during actuation of the relay1-12. Therefore, conditioned air is circuiated through the unit 16 tothe room 12 only upon the occurrence of one of the three conditionsnumbered above.

Attention is now directed to FIGURE 10 wherein there is shown anidealized graph of the manner in which the temperature in the room 12will be maintained during the coolness of a night during which thetemperature in the room 12 would drop substantially below T and duringan ensuing warm daytime period during which the temperature in the room12 would otherwise rise substantially above the temperature T It will beseen that the line 224 representing temperature oscillates above andbelow the line 226 representing a temperature of T during the intervalof time identified as night, and thereafter increases to a general levelwherein the same oscillates above and below the line 228 representingthe temperature T during the time interval designated as day. During theperiod of time during which the line 224- oscillates above and below theline 226, the temperature outside the room 12 is such that intermittentperiods of heating are required in order to maintain the room temperature about the level T During the portions of temperature oscillationwhen the line 224 is below the line 226, it will be understood that themercury switches 72 and 74 are in the positions shown thereof in FIGURE6 such that the burner 36 has a high heat output so that the unit 16 isfurnishing heat to the room 12. Inertial aspects of the heating systemresult in the temperature rising to levels somewhat above that indicatedby the line 226. With external temperatures rising as upon the change ofnight into day, there is no further need for heating, and the roomtemperature enters a period during which the same gradually increases tobe slightly above the temperature T represented by the line 226,whereupon the mercury switches 72 and 74 assume the positions shown inFIGURE 8, with the result that the burner system 36 is operated at itslow heating rate. During the course of the daytime period, cooling willbe intermittently demanded so that the temperature in the room 12 willrise and fall so as to oscillate above and below the temperature level Tas represented by the line 228. It will be noted that whenever thetemperature in the room 12 as sensed by the bimetallic strip 64 of thethermostat 24 lies between the temperatures T and T the mercury switches72 and 74 are in the positions shown thereof in FIGURES 7 and 9, duringwhich time the burner system 36 as well as the pump motor 34 isinactive. During such period, the blower motor 22 will be energized onlyif the air within the unit 16 is hot (immediately following a heatinginterval), or if the switch 204 is in the on position. Whenever thetemperature sensed by the thermostat 24 is below T the burner system 36is activated at its high heating rate and the blower motor 22 isenergized as soon as the air within the unit 16 has become heated;however, the pump motor 34 is de-energized whenever the temperature isbelow T and for that matter below T Whenever the temperature sensed bythe thermostat 24 exceeds T the burner system 36 is activated to its lowoutput heating rate, and the blower motor 22 and the pump motor 34 areenergized.

It has been previously mentioned that the principles of the instantinvention are applicable to the use of gas and L.P.G. fuels as well asto the burning of fuel oil. The foregoing description of a preferredembodiment of the invention as applied to the burning of fuel oil willmake this apparent to those skilled in the art. Where it is desired toburn either natural or manufactured gas as provided in gas mains orL.P.G. fuels, each of which are of course burned in a gaseous state, itis only necessary that the burner system 36 be such as to include aconventional gas combustion unit, rather than the described oil burner,with the air vents appropriately adjusted for the class of fuel that itburns. The leads 48 and 49 are in this modification applied tocontrolling a solenoid master shutoff valve in the fuel supply line,such that the shut-off valve is closed at all times except when theleads 48 and 49 are energized. Also, a solenoid fuel flow ratecontrolling valve downstream of the shut-off valve would be actuatablebetween two positions by means of a mechanical linkage to the armature56 controlled by the solenoid 54, the arrangement being such thatenergization of the leads 182 and 184 would cause the solenoid 54 toactuate the fuel flow controlling valve to a high flow rate position,with the valve returning to a low How rate position upon de-energizationof the solenoid 54.

Many other arrangements will readily occur to those skilled in the art.For example, two burners can be arranged in parallel with one of theburners arranged to operate solely when the leads 48 and 49 areenergized, with the other burner arranged to operate solely when theleads 182 and 184 are energized. With this alternate arrangement,cooling will occur during single burner op eration, and heating willoccur during dual burner operation.

From the foregoing, it will be appreciated that the disclosed apparatusis capable of controlling a conventional heating and cooling unit in anentirely automatic fashion so that the unit is operated as a heaterwhenever the temperature is below one temperature and as a cooling unitwhenever the temperature exceeds a somewhat higher temperature. Not onlyis the heating and cooling unit operated in such an automatic fashion,but auxiliary equipment such as the air circulation motor and thecoolant circulating motor are operated in proper coordination therewith.The advantages of such a fully automated control system for year-roundair conditioning purposes will be evident.

No further description of the apparatus is deemed necessary to a fulland complete understanding of the principles involved. The apparatus hasbeen described in rather elaborate detail in order to facilitate anunderstanding thereof, and restricted scope of invention is not to beimputed from such detailed description, but rather attention is directedto the appended claims in order to ascertain the actual scope of theinvention.

I claim:

1. Apparatus comprising in combination air heating means, air coolingmeans and temperature control means, said temperature control meansincluding first and second mercury switches, temperature sensitive meanscoupled to said mercury switches to rotate said switches on asubstantially horizontal axis in response to temperature changes, eachof said switches having a first and a second set of contacts at itsopposite ends, each of said first set of contacts being at the forwardend of its respective switch in relation to direction of switch rotationupon temperature change in one direction, each of said second set ofcontacts being at the forward end of its respective switch in relationto direction of switch rotation upon temperature change in the oppositedirection, said mercury switches being inclined with respect to eachother in the vertical plane so that one of said switches is moreforwardly inclined in the direction corresponding to rotation upontemperature change in one direction while the other of said switches ismore forwardly inclined in the direction corresponding to rotation upontemperature change in the opposite direction, said air heating meansactuated only upon closing of both of said first sets of contacts, saidair cooling means actuated only upon closing of both of said second setsof contacts, said air heating means and said air cooling means remainingoff during closure of only one of said first sets of contacts and onlyone of said second sets of contacts.

2. Apparatus comprising in combination air heating means, air coolingmeans and temperature control means, said temperature control meansincluding thermally sensitive means and first and second mercuryswitches, said thermally sensitive means coupled to the mercury switchesto rotate each of said switches about a substantially horizontal axis inresponse to temperature changes, each of said mercury switches having acentral conductor with first and second spaced contacts at its oppositeends, respectively, the first contact of each of the switches beingdisposed at the end of the switch that travels furthest downwardly uponrotation resulting from an increase in temperature, said mercuryswitches being inclined with respect to each other in the vertical planeso that one of said mercury switches is downwardly inclined in thedirection corresponding to rotation resulting from an increase intemperature to a greater extent that the other, electrical power supplymeans to said temperature control means, said temperature control meanshaving a first circuit including both of said first contacts in seriesand a second circuit including both of said second contacts in series,said air cooling means electrically connected to said temperaturecontrol means, said air cooling means actuated only upon completion ofsaid first circuit through each of said first contacts which occurs whenthe temperature is above a first predetermined value, said air heatingmeans electrically connected to said temperature control means, said airheating means actuated only upon completion of said second circuitthrough each of said second contacts which occurs when the temperatureis below a second predetermined value, and both said first and saidsecond circuits being open upon the temperature being between said firstpredetermined value and said second predetermined value.

3. Control apparatus comprising air heating means, air cooling means andtemperature control means, said temperature control means includingfirst and second single-pole, double-throw mercury switches, a thermallysensitive bimetallic element coupled to the mercury switches to rotatethe latter about a substantially horizontal axis in response totemperature. changes, each of said mercury switches having a centralconductor and first and second contacts at its opposite ends, the firstcontact of each of the switches being disposed at the end of the switchthat travels downwardly upon rotation resulting from an increase intemperature, said mercury switches being inclined with respect to eachother in the vertical plane with the first mercury switch beingdownwardly inclined in the direction corresponding to rotation resultingfrom an increase in temperature to a greater extent than the secondmercury switch, first and second electrical power leads, the first powerlead being connected to the second and first contacts of the first andsecond mercury switches, respectively, a first and a second electricalcontrol relay each including a normally deenergized solenoid, each ofthe solenoids of the first and second relays having one end connected tothe second power lead and their other ends connected to the first andsecond contacts of the first and second mercury switches, respectively,with the other end of the solenoid of the second relay also beingconnected to the second contact of the second mercury switch through anormally opened switch controlled by the first power relay, a leadconnecting the central conductors of the mercury switches, saidtemperature control means adapted to energize the solenoids of both thefirst and second relays upon the temperature being less than a selectedlower value and adapted to energize solely the solenoid of the secondrelay upon the temperature being more than a certain higher value, saidair heating means being actuated upon energization of the solenoids ofboth the first and second relays, said air cooling means being actuatedupon energization of solely the solenoid of the second relay, and bothsaid air heating means and said air cooling means being 01f when thetemperature is between said lower value and said higher value.

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